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Número de publicaciónUS3994860 A
Tipo de publicaciónConcesión
Número de solicitudUS 05/564,360
Fecha de publicación30 Nov 1976
Fecha de presentación2 Abr 1975
Fecha de prioridad3 Abr 1974
También publicado comoDE2514636A1
Número de publicación05564360, 564360, US 3994860 A, US 3994860A, US-A-3994860, US3994860 A, US3994860A
InventoresClaude Brousse
Cesionario originalRhone-Poulenc Industries
Exportar citaBiBTeX, EndNote, RefMan
Enlaces externos: USPTO, Cesión de USPTO, Espacenet
Process for improving the shrinkage resistance upon-drying membranes of sulphonated polyaryl ether by immersing the membrane in an aqueous solution of an inorganic salt of a carbonylated or hydroxylated lower carboxylic acid
US 3994860 A
Resumen
Sulphonated polyaryl ether membranes are rendered less susceptible to shrinkage during drying by immersing the membrane in a solution of an inorganic salt of a hydroxylated or carbonylated lower carboxylic acid.
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Reclamaciones(6)
We claim:
1. Process for treating a sulphonated polyaryl ether membrane which comprises immersing the membrane in an aqueous solution containing from 10% by weight to the saturation concentration of an inorganic salt which is soluble in water to an extent of at least 15% by weight of a hydroxylated or carbonylated lower carboxylic acid.
2. Process according to claim 1, in which the inorganic salt is a sodium or potassium salt.
3. Process according to claim 1, in which the lower carboxylic acid possesses at most 10 carbon atoms and is devoid of ethylenic double bonds.
4. Process according to claim 3, in which the carboxylic acid is lactic or citric acid.
5. Process according to claim 3, in which the carboxylic acid is selected from 2-hydroxy-isobutyric, gluconic, glycollic, glyoxylic, malic, mandelic and tartaric acid.
6. Process according to claim 3, in which the sulphonated polyaryl ether is a sulphonated polyaryl ether/sulphone.
Descripción

This invention relates to a process for treating a sulphonated polyaryl ether membrane, particularly for reverse osmosis or ultra-filtration.

Membranes suitable for reverse osmosis or ultrafiltration which are made from sulphonated polyethers, especially from sulphonated polyaryl ether sulphones are known [see, for example, U.S. Pat. No. 3,709,841 and French Pat. Nos. 2,138,333 and 2,138,334].

The sulphonated polyaryl ether/sulphones used for this purpose are generally polymers which comprise a plurality of units of the formula: ##STR1## and, optionally, units of the formula: ##STR2## in which: EACH OF E, G and G1, which may be identical or different, is an aromatic group, at least one of which is substituted by one or more sulphonic acid groups, it being possible for the number of sulphonic acid groups per aromatic group to vary from one unit to another,

Each of E', G' and G'1, which may be identical or different, are as defined under E, G and G1 except that they do not contain sulphonic acid groups,

Each of Q and Q1, which may be identical or different, represents a substitutent which is inert to sulphonation reactions, such as alkyl radicals with 1 to 4 carbon atoms, and halogen atoms, in particular fluorine, chlorine, bromine and iodine,

Each of Q2 and Q3, which may be identical or different, represents an electron-attracting group such as a nitro, phenylsulphone, alkylsulphone, trifluoromethyl, nitroso or pyridyl group,

Each of r, s, t and u, which may be identical or different, is 0 or an integer from 1 to 4, at least one of which is less than 4,

Each of m and n, which may be identical or different, is 0 or 1, and

R represents a valency bond or a radical which is --CO--, --O-- or --SO2 -- or a divalent organic hydrocarbon radical such as alkylene, alkylidene, cycloalkylene and arylene radicals, these radicals having preferably less than 7 carbon atoms.

The sulphonated polyaryl ether/sulphones described in U.S. Pat. No. 3,709,841 generally possess from 0.1 to 5 milliequivalents of sulphonic acid groups per gram (meq/g) of dry polymer.

These sulphonated polymers can be prepared by sulphonation (in known manner) of polyaryl ether/sulphones comprising a plurality of units of formula (II). The latter polymers can be prepared in accordance with the technique described in, for example, French Pat. No. 1,407,301.

It is also known (see the abovementioned United States patent) that membranes made from sulphonated polyaryl ether/sulphones are particularly useful for the fractionation of the various constituents of solutions by direct or reverse osmosis.

Asymmetric membranes made from sulphonated polyaryl ether/sulphones, prepared especially by casting a solution of polymer and then coagulating one of the faces of the film impregnated with solvent thus obtained, have also been described in the abovementioned United States patent. Such membranes possess a thin dense layer forming the active layer of the membrane, with a porous strengthening support layer.

A process for the preparation of symmetric semi-permeable membranes made from sulphonated polyaryl ether/sulphones, which can be used for fractionating the various constituents of a solution, especially by direct or reverse osmosis or by ultrafiltration, and which makes it possible to produce membranes which possess particularly advantgeous properties, in particular as regards their degree of rejection and flow rate, has been described in French Pat. No. 2,138,333. This process consists of forming a solution of a sulphonated polyaryl ether/sulphone, forming a film by casting this solution, immersing the supported film in a coagulation bath and then recovering the membrane thus produced. This process is characterised in that:

a. the sulphonated polyaryl ether/sulphone used possesses 0.1 to 2 meq/g of sulphonic acid groups and a reduced specific viscosity of 40 to 200 cm3 /g (measured using a 2 g/l solution in dimethylformamide [DMF] at 25° C),

b. the concentration of the solution for casting is from 5 to 60% (expressed in g of polymer per cm3 of solution),

c. the coagulation bath consists of water,

d. the temperature of the coagulation bath is 0° C to 100° C,

e. the duration of immersion in the coagulation bath is from 30 seconds to 60 minutes,

f. the immersion of the film in the coagulation bath is preceded by gelling this film, and

g. the solution of polymer and/or the coagulation bath contains 0.1 to 10% by weight of an amine salt or a quaternary ammonium salt which is soluble in water and in the solution of polymer.

This process is applicable to the various types of sulphonated polyaryl ether/sulphones containing units of formula I (and optionally II), it being understood that the expression "sulphonic acid" denotes a group of the formula

-SO3 -.1/n Mn +,

M denoting a hydrogen ion or an alkali metal or alkaline earth metal ion and n being 1 or 2.

Another process for the preparation of asymmetric semi-permeable membranes made from sulphonated polyaryl ether/sulphones has been described in French Pat. No. 2,138,334. This process consists of forming a solution of sulphonated polyaryl ether/sulphone, forming a film by casting the solution, immersing the support coated with the layer of polymer in a coagulating bath and then recovering the membrane, and it is characterised in that:

a. the sulphonated polyaryl ether/sulphone used possesses 0.3 to 2 meq/g of sulphonic acid groups and a reduced specific viscosity (measured as a 2 g/l solution of concentration in DMF at 25° C,) of 40 to 200 cm3 /g,

b. the concentration of the solution for casting is 5 to 60% (expressed in g of polymer per cm3 of solution),

c. the coagulating bath comprises, per 100 parts by weight of water, 5 to 100 parts of a salt formed from an anion of a strong inorganic acid and a metal cation and 1 to 120 parts of a solvent for the polymer.

d. the temperature of the coagulation bath is from -30° to +30° C,

e. the period of time for which the film is left in the coagulation bath is from 30 seconds to 60 minutes, and

f. the immersion of the film in the coagulation bath is preceded by gelling the film.

The membranes thus prepared, either in accordance with French Pat. No. 2,138,333 or in accordance with French Pat. No. 2,138,334, can then undergo additional treatments, especially heat treatments in water or aqueous saline solution, which, by tightening the structure of the said membranes, makes them more suitable for reverse osmosis.

The aim of the invention is to produce membranes made from sulphonated polyaryl ethers, more especially membranes for reverse osmosis made from sulphonated polyaryl ether/sulphones which, during drying, undergo only a small amount of dimensional shrinkage which prevents, or at least reduces, the danger of tearing when such membranes are dried after having been assembled in apparatuses.

It has been found, according to this invention, that this can be achieved by treating the membrane made from sulphonated polyaryl ether/sulphones by immersion in a solution of an inorganic (including ammonium [NH4 +]) salt of a lower carboxylic acid carrying hydroxyl or carbonyl groups.

The salts which can be used in the process of this invention are preferably sodium or potassium salts, are preferably salts which have a solubility in water of at least 15% by weight. The membranes are suitably immersed in aqueous solutions containing at least 10%, preferably at least 15% by weight up to the saturation concentration of the salt.

The lower carboxylic acids carrying hydroxyl or carbonyl groups are mono- or poly-carboxylic acids which generally possess at most 10 carbon atoms and are generally devoid of ethylenic double bonds; carbon atoms which do not form part of the carboxylic acid groups carry a carbonyl group or one or two hydroxyl groups. Lactic, citric, gluconic and tartaric acids, which are especially advantageous in numerous applications of the membranes because they are acceptable from the alimentary point of view, and 2-hydroxy-isobutyric, mandelic, glycollic, glyoxylic and malic acids may be mentioned as typical such carboxylic acids.

The duration of immersion in the salt solution acids is usually at least 30 seconds and preferably at least 2 minutes; there is no critical upper limit but it is generally of no value to prolong the immersion beyond 10 hours.

Once the immersion is complete, the membrane treated according to this invention can be dried in the ordinary way, for example simply by leaving it exposed to the atmosphere.

Of course, sulphonated polyethers other than sulphonated polyaryl ether/sulphones can be used in the invention; it is possible to treat membranes made from sulphonated polyarylene ethers in general.

The following Examples further illustrate the present invention. In these Examples, the membrane which is treated is a membrane made from a sulphonated polyaryl ether/sulphone (recurring unit [--C6 H4 --C(CH3)2 --C6 H4 --O--C6 H4 --SO2 --C6 H4 --O--]), prepared in accordance with French Pat. No. 2,138,333, and which, when used in reverse osmosis to treat a 5 g/l aqueous NaCl solution, under 30 bars at 20° C, possesses a degree of rejection of 95% for a flow rate of 500 l/day.m2.

The various membranes treated by means of the aqueous salt solutions (immersion for 4 hours at 20° C) are dried in air (removal of the drops of solutions which remain by simple contact with a sheet of filter paper, that is to say adsorbent paper, followed by drying by exposure to the atmosphere for 2 hours at 20° C) optionally followed by drying in vacuo (30 minutes at 25° C under an absolute pressure of 40 mm Hg).

After each of the drying operations, and without wetting again, the shrinkage shown by the membranes is measured.

The results obtained in the various Examples are given in the table below. The concentrations of solutions, expressed as a percentage, are concentrations in per cent by weight.

__________________________________________________________________________                                 Shrinkage in % after Nature of the           Concentration of the                      Shrinkage in % after                                 supplementary dryingExample treatment salt           treatment solution                      drying in air                                 in vacuo__________________________________________________________________________1     Potassium 35 %       1.4        1.4 lactate1bis(compara- None      0          11         11tive)2     Sodium lactate           35 %                  13     Sodium tartrate           Saturation 3.4        3.94     Sodium malate           35 %       1.4        2.75     Sodium citrate           35 %       0.7        26     Sodium glycollate           35 %       1.4        37     Sodium gluconate           35 %       2          2.48     Sodium glyoxylate           Saturation 2.7        3.79     Sodium mandelate           Saturation 1.4        1.4__________________________________________________________________________
Citas de patentes
Patente citada Fecha de presentación Fecha de publicación Solicitante Título
US3709841 *28 Abr 19709 Ene 1973Rhone Poulenc SaSulfonated polyarylethersulfones
US3717594 *19 Ene 197020 Feb 1973Ecodyne CorpStabilizing cation resins
US3855122 *19 May 197217 Dic 1974Rhone Poulenc SaProcess for the preparation of anisotropic semi-permeable membranes of polyaryl ether/sulphones
US3856556 *8 Mar 197324 Dic 1974Politechnika WarszawskaProcess for the manufacture of chemical resistant polyarylate films and coatings
US3875096 *20 Mar 19741 Abr 1975Us InteriorProcess for the preparation of a stable salt form of a sulfonated polyarylether sulfone
Citada por
Patente citante Fecha de presentación Fecha de publicación Solicitante Título
US4200726 *30 May 197829 Abr 1980Daicel Ltd.Semipermeable membrane of phenoxy resin containing sulfuric acid groups or salts thereof
US4208508 *7 Jul 197817 Jun 1980Asahi Kasei Kogyo Kabushiki KaishaSemipermeable membranes of polyaryl ether sulfones
US4292417 *20 Sep 197929 Sep 1981Daicel Ltd.Semipermeable membrane
US4414368 *27 Dic 19828 Nov 1983Albany International Corp.Chlorosulfonated polysulfones and derivatives thereof
US4521224 *16 Ene 19844 Jun 1985The Standard Oil CompanySemipermeable membranes prepared from polymers containing pendent sulfone groups
US4699634 *8 Jul 198513 Oct 1987The Standard Oil CompanyProcess for the modification of aromatic polymers via phase transfer catalysis to produce polyarylene polymers and the use thereof
US4717395 *7 Ago 19865 Ene 1988The Dow Chemical CompanyGas separations using membranes comprising sulphonated polyether sulphone
US4990252 *22 Ago 19895 Feb 1991HydanauticsStable membranes from sulfonated polyarylethers
US5624965 *26 Abr 199429 Abr 1997The Graver CompanyArylenedialkylidene polymers for high performance ion exchange membranes
US5685991 *12 Oct 199511 Nov 1997Pall CorporationIntegrity-testable wet-dry-reversible ultrafiltration membranes and method for testing same
US5788862 *12 Sep 19954 Ago 1998Pall CorporationFiltration medium
EP1466659A1 *10 Abr 200313 Oct 2004X-Flow B.V.A process for drying a wet porous membrane structure and the porous membrane structure obtained from said process
WO2004089520A1 *9 Abr 200421 Oct 2004Blume IngoA process for drying a wet porous membrane structure and the porous membrane structure obtained from said process
Clasificaciones
Clasificación de EE.UU.528/486, 210/500.41, 528/175, 528/174, 525/386, 210/500.33, 521/30, 521/27
Clasificación internacionalC08G65/48, C08G65/46, C08G75/00, B01D67/00, C08L71/12, B01D71/68, C25B13/04, C08G65/00, C08G75/23
Clasificación cooperativaB01D71/68, B01D2321/162, B01D65/08, B01D67/0088, C08G75/23
Clasificación europeaC08G75/23, B01D67/00R14, B01D65/08, B01D71/68